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(Cross posting from Sound design stack exchange since it was declared off topic there)

I have a sony speaker from an old Home Theatre System that is broken now leaving the standalone speakers in a good unused condition. I'm trying to design a Bluetooth capable audio unit to convert this into a nice Bluetooth speaker for my room. I need some help selecting the components for this project. Attached is an image of my speaker.

enter image description here

  1. How can I find the rated power of this speaker as I'm unable to find a proper datasheet or document on the internet that gives me this value. Is there a way to experimentally find out the power requirement of a speaker?
  2. The rated impedance is 3 Ω. I've found some amplifier modules (like PAM8430) on the internet but the specifications say that it can support 4 Ω and 8 Ω speakers can I still interface 3 Ω speakers and expect decent performance? Or is there a way I can increase the impedance of this speaker by adding some resistors etc or do I have to search for an amplifier that supports 3-ohm speakers?
  3. This speaker has +ve and =ve pins, can I directly connect these to the different parts of a 35mm TRS headphone jack or is some other kind of interfacing required?
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  • \$\begingroup\$ 1) You could look at how many watts the amplifier this was connected to can output to this speaker. 2) You can raise the impedance by putting a resistor in series, but that also means speaker is driven with much higher impedance. There is also a chance that 4 ohm capable amps can drive this 3 ohm speaker. 3) In general 3.5mm TRS connectors are not used for speaker connections, because it is too easy to connect something else to it instead of a speaker and have it damaged. Use connectors and terminals normally used for speakers, obviously. 4) Basically asking what to buy is off topic here. \$\endgroup\$ – Justme Feb 9 at 8:29
  • \$\begingroup\$ @Justme the amplifier previously driving this speaker was a part of a big home theatre setup and I don't think I can measure that. I guess I'll just try to drive it with the 4 ohm amplifier and see what happens \$\endgroup\$ – Sumanth Feb 9 at 8:37
  • \$\begingroup\$ Removed the product recommendation sub-question. These are off-topic here. \$\endgroup\$ – Marcus Müller Feb 9 at 8:44
  • \$\begingroup\$ Maybe you could point me to certain prominent websites where I can search for amplifiers based on their Impedance ratings? \$\endgroup\$ – Sumanth Feb 12 at 8:46
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Is there a way to experimentally find out the power requirement of a speaker?

That's less of a required than a maximum values. Go higher than that, and you damage the speaker; that's an easy experiment, but not very useful to you, unless you have spare speakers...

The rated impedance is 3 Ω … can support 4 Ω and 8 Ω speakers

Well, that's what ratings are for: to tell you what they promise will work. So, no, from that product page alone, this won't work.

It might be helpful to actually google for the PAM8430and find the original data sheet of the amplifier IC: It also doesn't specify operability at 3Ω. What it does say, however, is that the thing won't output more than 3W. Pretty certain a speaker your speaker's size can withstand that.

Also, a home theater speaker won't be very loud when driven with <= 3W. So, really not the amplifier you're looking for. This thing is designed to drive built-in laptop speakers and phone speakers. (datasheet, first page!)

It also specifies things for 10% THD and 1% THD only: This is not a Hifi component. So,

Or is there a way I can increase the impedance of this speaker by adding some resistors etc or do I have to search for an amplifier that supports 3-ohm speakers?

I'd recommend looking into better amplifiers, anyway, since you seem to be concerned with sound quality.

This speaker has +ve and =ve pins, can I directly connect these to the different parts of a 35mm TRS headphone jack or is some other kind of interfacing required?

Not quite sure what you mean here. TRS headphone jacks are not a sensible way to attach a large speaker to an amplifier: they are not designed for the high currents speakers can work with.

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  • \$\begingroup\$ Well, there was a 35 mm TRS mentioned. I expect it could carry more current than a standard 3.5mm TRS - if you can find a place to buy one. :) \$\endgroup\$ – JRE Feb 9 at 10:01
  • \$\begingroup\$ @JRE ah, good ole 35mm headphone jack, which can also double as explosive fuse holder, if you happen to have spare anti-aircraft ammunition. :D \$\endgroup\$ – Marcus Müller Feb 9 at 12:08

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